Method for separating halocarbons

ABSTRACT

The invention provides a method for separating halocarbons. In particular, a method for separating 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) from 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) based on differences in melting points of these compounds. More particularly the invention pertains to a method for separating HCFC-244bb from HCFO-1233xf which are useful as intermediates in the production of 2,3,3,3-tetrafluoropropene (HFO-1234yf).

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional patentapplication Ser. No. 61/091,034 filed Aug. 22, 2008, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention provides a method for separating halocarbons. Inparticular, the invention provides a method for separating2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) from2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) based on differences infreezing points of these compounds. More particularly the inventionpertains to a method for separating HCFC-244bb from HCFO-1233xf, whichare useful as intermediates in the production of2,3,3,3-tetrafluoropropene (HFO-1234yf).

2. Description of the Related Art

Fluorocarbon based fluids have found widespread use in industry in anumber of applications, including as refrigerants, aerosol propellants,blowing agents, heat transfer media, and gaseous dielectrics. Because ofthe suspected environmental problems associated with the use of some ofthese fluids, including the relatively high global warming potentialsassociated therewith, it is desirable to use fluids having the lowestpossible greenhouse warming potential in addition to zero ozonedepletion potential. Thus there is considerable interest in developingenvironmentally friendlier materials for the applications mentionedabove. Tetrafluoropropenes, having zero ozone depletion and low globalwarming potential, have been identified as potentially filling thisneed. However, the toxicity, boiling point, and other physicalproperties in this class of chemicals vary greatly from isomer toisomer. One tetrafluoropropene having valuable properties is2,3,3,3-tetrafluoropropene (HFO-1234yf). Thus, there is a need for newmanufacturing processes for the production of tetrafluoropropenes and inparticular 2,3,3,3-tetrafluoropropene.

HCFC-244bb and HCFO-1233xf are intermediates in the production of2,3,3,3-tetrafluoropropene (HFO-1234yf) which is well known in the artas described in U.S. Applications 20070007488 and 20070197842, thespecifications of which are incorporated herein by reference. HFO-1234yfhas been disclosed to be an effective refrigerant, heat transfer medium,propellant, foaming agent, blowing agent, gaseous dielectric, sterilantcarrier, polymerization medium, particulate removal fluid, carrierfluid, buffing abrasive agent, displacement drying agent and power cycleworking fluid.

Mixtures of two halocarbons are often inseparable using standardtechniques, especially when then form a binary azeotrope orazeotrope-like composition. The prior art has suggested various methodsof separating azeotropic mixtures of fluorocarbons. In this regardEuropean patent application EP 0 472 391 suggests separating HFC-134afrom a mixture containing hydrochlorofluorocarbons using an extractionagent such as trichloroethylene or perchloroethylene, among others. U.S.Pat. No. 5,211,817 attempts a separation of fluorocarbons fromazeotropic mixtures with HF by column distillation and withdrawing avapor side-stream followed by introducing the side-stream into arectifying column equipped with a condenser and operated at a highreflux ratio. These provide less than satisfactory solutions to theproblem.

It has now be found that individual halocarbons can be independentlyseparated from a composition of two different halocarbons by freezingthe composition at a temperature at or below the freezing point of thefirst halocarbon but above the freezing point of the second halocarbon.

HCFC-244bb and HCFO-1233xf are inseparable using conventional separationtechniques known in the art since HCFC-244bb and HCFO-1233xf form abinary azeotrope or azeotrope-like composition which is described inU.S. Provisional Application 61/040,759 filed Mar. 31, 2008, thespecification of which is incorporated herein by reference. It has beenfound that HCFC-244bb freezes at a temperature of about −78° C. whileHCFO-1233xf does not freeze at this temperature. When it is desired toseparate HCFC-244bb from HCFO-1233xf, the mixture of HCFC-244bb andHCFO-1233xf can be cooled to a temperature below the freezing point ofHCFC-244bb but above the freezing point of HCFO-1233xf and then the twocompounds can be separated by removing liquid or gaseous HCFO-1233xffrom solid HCFC-244bb by decantation, filtration, use of centrifuge, orother means known in the art. Essentially pure HCFC-244bb andHCFO-1233xf can be recovered.

SUMMARY OF THE INVENTION

The invention provides a method for isolating a first halocarbon from acomposition comprising a first halocarbon and at least one secondhalocarbon which is different from the first halocarbon, the methodcomprising cooling a composition comprising a first halocarbon and atleast one second halocarbon at or below the freezing point of the firsthalocarbon but above the freezing point of the at least one secondhalocarbon.

The invention also provides a method for the production of2,3,3,3-tetrafluoropropene which comprises

(i) continuously reacting 2-chloro-3,3,3-trifluoropropene with hydrogenfluoride, in a liquid phase reaction, in the presence of a liquid phasefluorination catalyst to produce a composition comprising unreacted HF,unreacted 2-chloro-3,3,3-trifluoropropene, and2-chloro-1,1,1,2-tetrafluoropropane; and then

(ii) isolating an azeotrope or azeotrope-like composition of2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene;and then

(iii) isolating 2-chloro-1,1,1,2-tetrafluoropropane from the azeotropeor azeotrope-like composition by cooling the azeotrope or azeotrope-likecomposition at or below the freezing point of2-chloro-1,1,1,2-tetrafluoropropane but above the freezing point of2-chloro-3,3,3-trifluoropropene; and then

(iv) dehydrochlorinating the isolated2-chloro-1,1,1,2-tetrafluoropropane under conditions effective toproduce 2,3,3,3-tetrafluoropropene; and

(v) optionally, recycling the isolated 2-chloro-3,3,3-trifluoropropeneback to the reaction of step (i).

DETAILED DESCRIPTION OF THE INVENTION

In the process of the instant invention, one commences with a mixture ofa first halocarbon and at least one second halocarbon. The mixture maybe an azeotrope, but this condition is not necessary. The thermodynamicstate of a fluid is defined by its pressure, temperature, liquidcomposition and vapor composition. For a true azeotropic composition,the liquid composition and vapor phase are essentially equal at a giventemperature and pressure. In practical terms this means that thecomponents cannot be separated during a phase change. For the purpose ofthis invention, an azeotrope is a liquid mixture that exhibits a maximumor minimum boiling point relative to the boiling points of surroundingmixture compositions. An azeotrope or an azeotrope-like composition isan admixture of two or more different components which, when in liquidform under given pressure, will boil at a substantially constanttemperature, which temperature may be higher or lower than the boilingtemperatures of the components and which will provide a vaporcomposition essentially identical to the liquid composition undergoingboiling. For the purpose of this invention, azeotropic compositions aredefined to include azeotrope-like compositions which mean compositionsthat behave like azeotropes, i.e., have constant-boiling characteristicsor a tendency not to fractionate upon boiling or evaporation. Thus, thecomposition of the vapor formed during boiling or evaporation is thesame as or substantially the same as the original liquid composition.Hence, during boiling or evaporation, the liquid composition, if itchanges at all, changes only to a minimal or negligible extent. This isin contrast with non-azeotrope-like compositions in which during boilingor evaporation, the liquid composition changes to a substantial degree.Accordingly, the essential features of an azeotrope or an azeotrope-likecomposition are that at a given pressure, the boiling point of theliquid composition is fixed and that the composition of the vapor abovethe boiling composition is essentially that of the boiling liquidcomposition, i.e., essentially no fractionation of the components of theliquid composition takes place. Both the boiling point and the weightpercentages of each component of the azeotropic composition may changewhen the azeotrope or azeotrope-like liquid composition is subjected toboiling at different pressures. Thus, an azeotrope or an azeotrope-likecomposition may be defined in terms of the relationship that existsbetween its components or in terms of the compositional ranges of thecomponents or in terms of exact weight percentages of each component ofthe composition characterized by a fixed boiling point at a specifiedpressure.

The first halocarbon and at least one second halocarbon in thecomposition may each independently be a fluorocarbon (FC), ahydrofluorocarbon (HFC), a hydrofluoroolefin (HFO), a chlorocarbon (CC),a hydrochlorocarbon (HCC), fluorochlorocarbon (FCC), ahydrochlorofluorocarbon (HCFC), a hydrofluoroether (HFE), or ahydrochlorofluoroolefin (HCFO), provided that the second halocarbon is adifferent from the first halocarbon. In one embodiment, the firsthalocarbon and the at least one second halocarbon form an azeotrope orazeotrope-like composition. In another embodiment the first halocarbonand the second halocarbon do not form an azeotrope or azeotrope-likecomposition. As examples, the first halocarbon and at least one secondhalocarbon in the composition may each independently be a compound ofthe Formula (I) and/or Formula (II), provided the first halocarbon andthe at least one second halocarbon are different, and the freezing pointof the first halocarbon is above the freezing point of the at least onesecond halocarbon.

Formula (I)—is a haloalkane having the formula C_(y)H_(z)X, whereinX═F_(a)Cl_(b)Br_(c)I_(d) having one or more halogen atoms, or acombination of different halogen atoms independently selected from F,Cl, Br, I with the total number of halogen atoms equals to 2y+2−z; y isan integer of from 1 to 4; and z is an integer of from 0 to 9 such thatz=2y+1; a, b, c, d are each an integer of from 1 to 10 and whereina+b+c+d=2y+2−z. Formula (II)—is a haloalkene having the formulaC_(y)H_(z)X, where X═F_(a)Cl_(b)Br_(c)I_(d) one or more halogen atoms,or a combination of different halogen atoms independently selected fromF, Cl, Br, I with the total number of halogen atoms equals to 2y−z; y isan integer of from 1 to 4; and z is an integer of from 0 to 7 such thatz ranges from 0 to 2y−1; a, b, c, d are each an integer of from 1 to 8and wherein a+b+c+d=2y−z.

Non-limiting examples of halocarbons include2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb);2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), trans1,2-dichloroethylene, pentafluorobutane; pentafluoropropane;hexafluoropropane; and heptafluoropropane;1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124); and pentafluoroethane(HFC-125); as well as 1,1-dichloro-1-fluoroethane (HCFC-141b)1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane(HFC-134a); 1-chloro 1,1-difluoroethane (HCFC-142b);1,1,1-trifluoroethane (HFC-143a); 1,1-dichloro-2,2,2-trifluoroethane(HCFC-123); 1,2-dichloro-1,2,2-trifluoroethane (HCFC-123a);1,1,1,3,3-pentafluorobutane (HFC-365mfc);1,1,1,2,3,3,3-heptafluoropropane (HCF-227ea); trichlorofluoromethane(CFC-1), dichlorodifluoromethane (CFC-12); 1,1,1,3,3,3-hexafluoropropane(HFC-236fa); 1,1,1,2,3,3-hexafluoropropane (HFC-236ea); difluoromethane(HFC-32); chlorofluoromethane (HCFC-31); difluoroethane (HFC-152a);1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,2,3-pentafluoropropane(HFC-245eb); 1,1,1,2,2-pentafluoropropane (HFC-245cb),trifluoropropenes, pentafluoropropenes, chlorotrifluoropropenes,hydrofluoroethers, and tetrafluoropropenes including1,3,3,3-tetrafluoropropene (HFO-1234ze), 2,3,3,3-tetrafluoropropene(HFO-1234yf), 1,2,3,3,3-pentafluoropropene (HFO-1225ye), and1-chloro-3,3,3-trifluoropropene (HCFC-1233zd).

The present invention provides a composition which comprises effectiveamounts of a first halocarbon and at least one second halocarbon. Byeffective amount is meant an amount of each component which, whencombined with the other component, results in the formation of ahomogeneous mixture, and preferably an azeotropic or azeotrope-likecomposition. In one embodiment the compositions preferably are binaryazeotropes which consist essentially of combinations of only the firsthalocarbon and a second halocarbon.

In one embodiment, the composition contains from about 1 to about 99weight percent of the first halocarbon, preferably from about 1 weightpercent to about 50 weight percent of the first halocarbon based on theweight of the overall composition. In one embodiment, the compositioncontains from about 1 to about 99 weight percent of the secondhalocarbon, preferably from about 50 weight percent to about 99 weightpercent of at least one second halocarbon based on the weight of theoverall composition.

After a mixture of first halocarbon and the at least one secondhalocarbon is separated from impurities, the mixture can be cooled tothe temperature below the freezing point of the first halocarbon butabove the freezing point of the at least one second halocarbon. In oneembodiment a temperature difference between the freezing point of thefirst halocarbon and the freezing point of the second halocarbon isabout 3° C. or more. In one embodiment the cooling is conducted at atemperature of from about −150° C. to about 75° C. In another embodimentthe cooling is conducted at a temperature of from about −130° C. toabout 50° C. In another embodiment the cooling is conducted at atemperature of from about −120° C. to about 25° C. The result of thecooling is the first halocarbon in solid form and the second halocarbonin liquid or gaseous form. A preferred step comprises the subsequentstep of separating the liquid or gaseous second halocarbon from thesolid first halocarbon. Essentially pure solid first halocarbon can berecovered by decantation, filtration, centrifugation, degassation undervacuum or by other means known in the art.

In one particularly preferred embodiment, the first halocarbon is2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) and the secondhalocarbon is 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and whereinthese form an azeotrope or azeotrope-like composition.

In a method of preparing a HCFC-244bb precursor, reagents arefluorinated with hydrogen fluoride. This may be done, for example, bythe liquid phase or gas phase catalytic fluorination of CF₃CCl═CH₂(HCFO-1233xf) with HF to yield HCFC-244bb. The reaction products of suchprecursors include HCFC-244bb, unreacted HCFO-1233xf, unreacted HF andother by-products. Upon removal of the by-products and HF, a binaryazeotrope or azeotrope-like composition of HCFC-244bb and HCFO-1233xf isformed as disclosed in U.S. Provisional Application 61/040,759 filedMar. 31, 2008. This binary azeotrope or azeotrope-like composition isthen available for separation into its component parts by the method ofthis invention. Then essentially pure HCFC-244bb can be fed into adehydrochlorination reactor to make HFO-1234yf and essentially pureHCFO-1233xf can optionally be recycled back to a fluorination reactor toproduce HCFC-244bb.

After a mixture of HCFC-244bb and HCFO-1233xf is separated fromimpurities, the mixture can be cooled to the temperature below thefreezing point of HCFC-244bb (about −78° C., the temperature of acetoneand dry ice) but above the freezing point of HCFO-1233xf. The result ofthe cooling is solid HCFC-244bb and liquid or gaseous HCFO-1233xf. Thenessentially pure solid HCFC-244bb can be recovered by decantation,filtration, centrifugation, degassation under vacuum or by other meansknown in the art.

In one embodiment, the mixture of HCFC-244bb and HCFO-1233xf is injectedinto a vessel maintained at temperature from about from about −85° C. toabout −75° C.; preferably from about −81° C. to about −78° C. ThenHCFO-1233xf is removed from the vessel by filtration. After heating thevessel to the temperature above freezing point of HCFC-244bb essentiallypure liquid HCFC-244bb can be recovered.

In another embodiment, the mixture of HCFC-244bb and HCFO-1233xf isinjected into a vessel maintained at temperature from about −81° C. toabout −78° C. Then essentially HCFC-244bb is separated from essentiallypure liquid HCFO-1233xf using a centrifuge.

In one preferred embodiment, the invention relates to a multistepprocess in which the above described process to isolate HCFC-244bb fromHCFO-1233xf is preceded by a prior process step for producing2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) by liquid phasefluorination of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) withhydrogen fluoride to produce a stream comprising hydrogen fluoride,2-chloro-1,1,1,2-tetrafluoropropane, and2-chloro-3,3,3-trifluoropropene.

In the practice of the present invention, a liquid phase catalyst asdescribed below is charged into a fluorination reactor prior to heatingthe reactor. Any reactor suitable for a fluorination reaction may beused in the invention. Preferably the reactor is constructed frommaterials which are resistant to the corrosive effects of HF such asHastelloy-C, Inconel, Monel and fluoropolymer-lined vessels. Such liquidphase fluorination reactors are well known in the art. Then the HF andHCFO-1233xf are fed to the reactor after the reactor reaches the desiredtemperature. In the preferred embodiment, the reaction is conducted at atemperature of from about 30° C. to about 200° C., more preferably fromabout from about 50° C. to about 150° C., and still more preferably fromabout 75° C. to about 125° C. The pressure of the reaction variesdepending on the temperature, quantity of hydrogen chloride and hydrogenfluoride used, and conversion of HCFO-1233xf. Convenient operatingpressure ranges from about 5 psia to about 200 psia, and preferably from30 to about 175 psia, and most preferably about 60 psia to about 150psia.

In the preferred embodiment, the catalyst is present in an amount offrom about 2% to about 80%, and preferably from about 5% to about 50%,and most preferably from about 10% to about 20%, based on the molepercent of HCFO-1233xf. Fluorination catalysts having a purity of atleast 98% are preferred.

Based on reaction stoichiometry, the required mole ratio of HF toHCFO-1233xf is at least equal to the number of double bonds in thestarting organic material and preferably is present in an excess. In thepreferred embodiment, the mole ratio of HF to HCFO-1233xf ranges from atleast about 1:1 to about 50:1, more preferably from about 1:1 to about30:1 and most preferably from about 2:1 to about 15:1. Any water in theHF will react with and deactivate the catalyst. Therefore substantiallyanhydrous HF is preferred. By “substantially anhydrous” is meant thatthe HF contains less than about 0.05 weight % water and preferablycontains less than about 0.02 weight % water. However, one of ordinaryskill in the art will appreciate that the presence of water in thecatalyst can be compensated for by increasing the amount of catalystused. HF suitable for use in the reaction may be purchased fromHoneywell International Inc. of Morristown, N.J.

Any liquid phase fluorination catalyst may be used in the invention. Anon-exhaustive list includes Lewis acids, transition metal halides,transition metal oxides, Group IVb metal halides, a Group Vb metalhalides, or combinations thereof. Non-exclusive examples of liquid phasefluorination catalysts are an antimony halide, a tin halide, a tantalumhalide, a titanium halide, a niobium halide, and molybdenum halide, aniron halide, a fluorinated chrome halide, a fluorinated chrome oxide orcombinations thereof. Specific non-exclusive examples of liquid phasefluorination catalysts are SbCl₅, SbCl₃, SbF₅, SnCl₄, TaCl₅, TiCl₄,NbCl₅, MoCl₆, FeCl₃, a fluorinated species of SbCl₅, a fluorinatedspecies of SbCl₃, a fluorinated species of SnCl₄, a fluorinated speciesof TaCl₅, a fluorinated species of TiCl₄, a fluorinated species ofNbCl₅, a fluorinated species of MoCl₆, a fluorinated species of FeCl₃,or combinations thereof.

These catalysts can be readily regenerated by any means known in the artif they become deactivated. One suitable method of regenerating thecatalyst involves flowing a stream of chlorine through the catalyst. Forexample, from about 0.002 to about 0.2 lb per hour of chlorine can beadded to the liquid phase reaction for every pound of liquid phasefluorination catalyst. This may be done, for example, for from about 1to about 2 hours or continuously at a temperature of from about 65° C.to about 100° C.

The resulting HCFC-244bb and unreacted HCFO-1233xf can be recovered fromthe reaction mixture (HCFC-244bb, HCFO-1233xf, HF and impurities) viaany separation or purification method known in the art such asneutralization and distillation. The HCFC-244bb is then isolated by themethod of the present invention. HCFC-244bb in an essentially pure formis used as an intermediate in the production of2,3,3,3-tetrafluoropropene HFO-1234yf. The process of the invention maybe carried out either in a batch or continuous mode. In a continuousprocess, the HCFO-1233xf and HF are preferably fed simultaneously to thereactor after the reactor reaches the desired temperature. Thetemperature and pressure of the fluorination reaction remain essentiallythe same for both the batch and continuous modes of operation. Theresidence time or contact time, varies from about 1 second to about 2hours, preferably from about 5 seconds to about 1 hour and mostpreferably from about 10 seconds to about 30 minutes. A sufficientquantity of catalyst must be present to affect the fluorination in theresidence times described above. In a continuous mode of operation,HCFC-244bb, unreacted HCFO-1233xf, and unreacted HF are continuouslyremoved from the reactor.

In a preferred embodiment, the invention relates to a multistep processin which the above described process to isolate HCFC-244bb fromHCFO-1233xf is followed by a subsequent process step for producing2,3,3,3-tetrafluoropropene (HFO-1234yf) by vapor or liquid phasedehydrochlorination of 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb)in the presence of a catalyst or caustic solution to produce a streamcomprising 2,3,3,3-tetrafluoropropene and HCl.

The catalytic conversion of HCFC-244bb is conducted under conditionseffective to dehydrochlorinate HCFC-244bb to produce2,3,3,3-tetrafluoropropene (HFO-1234yf. Preferably dehydrochlorinationof HCFC-244bb is done in a vapor phase, and more preferably in afixed-bed reactor in the vapor phase. The dehydrochlorination reactionmay be conducted in any suitable reaction vessel or reactor, but itshould preferably be constructed from materials which are resistant tothe corrosive effects of hydrogen chloride (to the extent that suchmaterial is formed under the dehydrochlorination conditions) such asnickel and its alloys, including Hastelloy, Inconel, Incoloy, and Monelor vessels lined with fluoropolymers and may employ single or multipletubes packed with a dehydrochlorination catalyst.

Catalysts for HCFC-244bb Dehydrochlorination to HFO-1234yf.

The catalysts may be metal halides, halogenated metal oxides, neutral(or zero oxidation state) metal or metal alloy, or activated carbon inbulk or supported form. When metal halides or metal oxides catalysts areused, preferably mono-, bi-, and tri-valent metal halides, oxide andtheir mixtures/combinations, and more preferably mono-, and bi-valentmetal halides and their mixtures/combinations. Component metals include,but are not limited to, Cr³⁺, Fe³⁺, Mg²⁺, Ca²⁺, Ni²⁺, Zn²⁺, Pd²⁺, Li⁺,Na⁺, K⁺, and Cs⁺. Component halogens include, but are not limited to,F⁻, Cl⁻, Br⁻, and I⁻. Examples of useful mono- or bi-valent metal halideinclude, but are not limited to, LiF, NaF, KF, CsF, MgF₂, CaF₂, LiCl,NaCl, KCl, and CsCl. Halogenation treatments can include any of thoseknown in the prior art, particularly those that employ HF, F₂, HCl, Cl₂,HBr, Br₂, HI, and I₂ as the halogenation source.

When neutral, i.e., zero valent, metals, metal alloys and their mixturesare used. Useful metals include, but are not limited to, Pd, Pt, Rh, Fe,Co, Ni, Cu, Mo, Cr, Mn, and combinations of the foregoing as alloys ormixtures. The catalyst may be supported or unsupported. Useful examplesof metal alloys include, but are not limited to, SS 316, Monel 400,Inconel 825, Inconel 600, and Inconel 625.

The HCFC-244bb is introduced into the reactor either in pure form,partially purified form, or as part of the reactor effluent from thepreceding step. The HCFC-244bb may optionally be fed with an inert gasdiluent such as nitrogen, argon, or the like. In a preferred embodimentof the invention, the HCFC-244bb is pre-vaporized or preheated prior toentering the reactor. Alternately, the HCFC-244bb is vaporized insidethe reactor. Useful reaction temperatures may range from about 100° C.to about 700° C. Preferred temperatures may range from about 150° C. toabout 600° C., and more preferred temperatures may range from about 200°C. to about 550° C. The reaction may be conducted at atmosphericpressure, super-atmospheric pressure or under vacuum. The vacuumpressure can be from about 5 torr (0.0966 psig) to about 760 torr (14.69psig). Contact time of the HCFC-244bb with the catalyst may range fromabout 0.5 seconds to about 120 seconds, however, longer or shorter timescan be used.

Preferably in such dehydrochlorination embodiments as described in thissection, the conversion of the HCFC-244bb is at least about 10%, morepreferably at least about 20%, and even more preferably at least about30%. Preferably in such embodiments, the selectivity to HFO-1234yf, isat least about 70%, more preferably at least about 85% and morepreferably at least about 95%.

In the preferred embodiment, the process flow is in the down or updirection through a bed of the catalyst. It may also be advantageous toperiodically regenerate the catalyst after prolonged use while in placein the reactor. Regeneration of the catalyst may be accomplished by anymeans known in the art, for example, by passing air or air diluted withnitrogen over the catalyst at temperatures of from about 100° C. toabout 400° C., preferably from about 200° C. to about 375° C., for fromabout 0.5 hour to about 3 days.

In general, the effluent from the dehydrochlorination reaction step,including any intermediate effluents that may be present in multi-stagereactor arrangements, may be processed to achieve desired degrees ofseparation and/or other processing. For example, in embodiments in whichthe reactor effluent comprises HFO-1234yf, the effluent will generallyalso include HCl and unreacted HCFC244bb. Some portion or substantiallyall of these components of the reaction product may be recovered fromthe reaction mixture via any separation or purification method known inthe art such as neutralization and distillation. It is expected thatunreacted HCFC-244bb could be recycled, completely or partially, toimprove the overall yield of the desired CF₃CF═CH₂ (HFO-1234yf).Optionally, but preferably, hydrogen chloride is then recovered from theresult of the dehydrochlorination reaction. Recovering of hydrogenchloride is conducted by conventional distillation where it is removedfrom the distillate.

Alternatively, HCl can be recovered or removed by using water or causticscrubbers. When a water extractor is used HCl is removed as an aqueoussolution. When caustic is used, HCl is just removed from system as achloride salt in aqueous solution.

In an alternate embodiment of the invention, dehydrochlorination ofHCFC-244bb can also be accomplished by reacting it with a strong causticsolution that includes, but is not limited to KOH, NaOH, Ca(OH)₂ and CaOat an elevated temperature. In this case, the strength of the causticsolution is of from about 2 wt % to about 100 wt %, more preferably fromabout 5 wt % to about 90 wt % and most preferably from about 10 wt % toabout 80 wt %. The caustic to HCFC-244bb mole ratio preferably rangesfrom about 1:1 to about 2:1; more preferably from about 1.1:1 to about1.5:1 and most preferably from about 1.2:1 to about 1.4:1. The reactionmay be conducted at a temperature of from about 20° C. to about 100° C.,more preferably from about 30° C. to about 90° C. and most preferablyfrom about 40° C. to about 80° C. As above, the reaction may beconducted at atmospheric pressure, super-atmospheric pressure or undervacuum. The vacuum pressure can be from about 5 torr (0.0966 psig) toabout 760 torr (14.69 psig). In addition, a solvent or phase transfercatalyst such as Aliquat 336 may optionally be used to help dissolve theorganic compounds in the caustic solution. This optional step may beconducted using solvents that are well known in the art for saidpurpose. Thereafter, HFO-1234yf may be recovered from the reactionproduct mixture comprised of unreacted starting materials andby-products by any means known in the art, such as by extraction andpreferably distillation. The mixture of HFO-1234yf and any by-productsare passed through a distillation column. For example, the distillationmay be preferably conducted in a standard distillation column atatmospheric pressure, super-atmospheric pressure or a vacuum. Preferablythe pressure is less than about 300 psig, preferably less than about 150psig and most preferably less than 100 psig. The pressure of thedistillation column inherently determines the distillation operatingtemperature. Preferably in such dehydrochlorination embodiments asdescribed in this section, the conversion HCFC-244bb is at least about60%, more preferably at least about 75%, and even more preferably atleast about 90%. Preferably in such embodiments, the selectivity toHFO-1234yf, is at least about 70%, more preferably at least about 85%and more preferably at least about 95%.

The following non-limiting examples serve to illustrate the invention.

Example 1

An ebulliometer comprising a vacuum jacketed tube with a condenser ontop which is further equipped with a Quartz Thermometer is used. About20.91 g HCFO-1233xf is charged to the ebulliometer and then HCFC-244bbis added in small, measured increments. Temperature depression isobserved when HCFC-244bb is added to HCFO-1233xf, indicating a binaryminimum boiling azeotrope is formed. From greater than about 0 to about5 weight percent 244bb, the boiling point of the composition stays belowor around the boiling point of 1233xf. The boiling temperature ofHCFO-1233xf (98% pure) is about 9.82° C. at 14.4 psia, and the boilingof TOX grade HCFO-1233xf (99.99% pure) is about 12° C. at 14.5 psia. Theboiling point of HCFC-244bb is about 14.0 at 14.5 psia. The binarymixtures shown in Table 1 were studied. The compositions exhibitazeotrope and/or azeotrope-like properties over this range.

TABLE 1 HCFO-1233xf/HCFC-244bb Compositions at P = 14.4 psia. Wt. % Wt.% T (° C.) HCFO-1233xf HCFC- 244bb 9.79 98.35 1.65 9.78 96.54 3.46 9.7894.83 5.17 9.85 93.18 6.82 9.95 91.11 8.89 10.00 87.45 12.45 10.25 83.9116.09 10.36 80.86 19.14 10.43 76.37 23.63

Example 2

The vapor pressure of pure HCFO-1233xf, HCFC-244bb and 50/50% mixture ofHCFO-1233xf/HCFC-244bb was measured. The result in Table 2 shows thatthe vapor pressure of this mixture is higher than the vapor pressure ofeither pure component HCFO-1233xf, and HCFC-244bb at 0, 25 and 60° C.

TABLE 2 Vapor Pressure of HCFO-1233xf/HCFC-244bb mixture Wt. %HCFO-1233xf/ T (° C.) Pressure (Psia) HCFC-244bb 0.0 8.87 100.0/0.0 9.43 50.0/50.0 8.24  0.0/100.0 25.0 22.88 100.0/0.0  23.81 50.0/50.021.33  0.0/100.0 60.0 64.58 100.0/0.0  64.98 50.0/50.0 59.75  0.0/100.0

Example 3

A 500 cm³ Teflon cylinder was charged with 100 grams of HCFC-244bb. Thecylinder was placed into the Dewar filled with Acetone and Dry Icemixture (temperature about −78° C.). After 1 hour the cylinder wasremoved from the Dewar and HCFC-244bb was observed to be frozen.

Example 4

A 500 cm³ Teflon cylinder was charged with 81 grams of HCFC-244bb andHCFO-1233xf mixture. The cylinder was placed into the Dewar filled withEthanol and Dry Ice mixture (temperature about −78° C.). After 1 hourthe cylinder was removed from the Dewar and a liquid layer was observedon top of a solid layer. The cylinder was then placed into the cold bathfor an additional 1 hour. Then the liquid was transferred into an emptyevacuated cylinder. GC analysis of this liquid showed that it wasenriched in HCFO-1233xf relative to the initial mixture charged into theTeflon cylinder.

Example 5

A filtration vessel equipped with a cooling system is charged with aHCFC-244bb and HCFO-1233xf mixture. The vessel is cooled to about −78°C. to −85° C. and essentially pure HCFC-244bb is then recovered byremoving HCFO-1233xf from the vessel by filtration.

Example 6

A 500 cm³ stainless steel cylinder is charged with 100 grams ofrefrigerant R410A which is a 50/50 wt % azeotropic mixture ofpentafluoroethane (HFC-125) (FP═−103° C.) and difluoromethane (HFC-32)(FP═−136° C.). The cylinder is placed into a low temperature chamberthat is capable of achieving a temperature about that of liquid nitrogen(−196° C.). The chamber is equipped with a temperature control systemusing liquid N₂ as the coolant. The cylinder is cooled to about −110° C.which freezes the HFC-125 component of the mixture. Then the liquidportion of the sample is transferred into an empty evacuated cylinder.GC analysis of this liquid shows that it is highly enriched in HFC-32relative to the initial mixture charged into the cylinder.

Example 7

A 500 cm³ stainless steel cylinder is charged with 200 grams ofrefrigerant R407c which is a ternary mixture of HFC-32 (FP═−136°C.)/HFC-125 (FP═−103° C.)/HFC-134a (FP═−101° C.). The composition of themixture is 38/18/44 mole % respectively. The cylinder is placed into thesame low temperature chamber as in Example 6. The cylinder is cooled toabout −110° C. which freezes the HFC-125 and HFC-134a components of themixture. Then the liquid portion of the sample is transferred into anempty evacuated cylinder. GC analysis of this liquid shows that it ishighly enriched in HFC-32 relative to the initial mixture charged intothe cylinder.

Example 8

This example illustrates the continuous liquid phase hydrofluorinationreaction of 2-chloro-3,3,3-trifluoropropene(HCFO-1233xf)+HF→2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb)

About 4255 grams of SbCl₅ were contained in a Teflon™-lined liquid phasereactor (Teflon is a trademark of E.I. duPont de Nemours & Co) equippedwith a 2-inch ID (inside diameter) packed column and a condenser. Thereactor was 2.75-inch ID×36-inch L (length). Initially, a greater than5:1 mole ratio of HF was added to the reactor to fluorinate thecatalyst. A greater than 3:1 mole ratio of Cl₂ was then added to thereactor to ensure that the catalyst was brought back to a pentavalentstate. The reactor was heated to about 85° C.-87° C. HF feed was startedfirst. After about 1.5 lbs of HF had been added, the2-chloro-3,3,3-trifluoropropene feed was started. The purity of the2-chloro-3,3,3-trifluoropropene feed stock was about 97.3 GC area %. Theexperiment ran continuously for 71 hours. For this run, Cl₂ was fedbatchwise about every 4 hours throughout the run to keep the catalystactive.

The experiment was run for a total of 38.75 hours. A total of 45.1pounds of HCFO-1233xf was fed during the run. For the first 11.75 hoursthe average HCFO-1233xf feed rate was 0.62 lb/hr and the HF feed rateaveraged 0.73 lb/hr. This is a mole ratio of HF to HCFO-1233xf of 7.7to 1. The feed rates were increased to an average of 1.38 lb/hr ofHCFO-1233xf and 1.53 lb/hr of HF for the next 16.25 hours. This is amole ratio of HF to HCFO-1233xf of 7.2 to 1. The organic feed wasreduced slightly for the next 11.75 hrs to an average of 1.31 lb/hr. TheHF feed rate stayed the same as the previous 16.25 hours of on-streamtime. The mole ratio of HF to HCFO-1233xf increased to 7.6 to 1.

For the first 11.75 hours the HCFO-1233xf conversion on a molar basisaveraged 97.6% excluding the 1^(st) couple of samples (before steadystate was achieved). The selectivity (molar basis) of HCFC-244bbaveraged 97.1%.

For the next 16.25 hours the HCFO-1233xf conversion on a molar basisaveraged 88.9% and the selectivity (molar basis) of HCFC-244bb averaged95.8%. During this time the Cl₂ addition frequency was increased fromadding every 4 hr to once every 3 hr. This had no effect on theHCFO-1233xf conversion or the 244bb selectivity which leads one tobelieve that the 3-4 wt % Cl₂ to organic ratio that was chosen issufficient to keep the catalyst active and adding extra Cl₂ (adding itmore frequently) only adds to an increase in the amount of HCFO-1223xdfor some period of time after the Cl₂ addition.

Finally, for the last 11.75 hours the HCFO-1233xf conversion on a molarbasis averaged 92.3% and the selectivity (molar basis) of HCFC-244bbaveraged 96.4%.

The reactor temperature range for the experiment was 78° C.-86° C. andthe pressure range was 70 psig-105 psig. The organic crude materialcollected from the run was run on a gas chromatograph and exhibited thefollowing GC analysis. The following Table 3 sets forth the2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) conversion and productselectivity data.

TABLE 3 (Conversion and Selectivity on a Molar Basis) molar molar molarmolar molar hours selectivity selectivity Conversion % selectivityselectivity molar elapsed Temp HFC- HCFC- HCFO- HCFC- HCFO- selectivityTime (° C.) 245cb 244bb 1233xf 235da 1223xd others 1 84.1 8.6 87.6 94.50.0 0.2 3.6 2 85 1.3 98.3 93.8 0.0 0.0 0.3 4 85.2 0.6 96.5 94.8 0.0 1.01.9 5 85.6 4.3 90.8 92.6 0.0 0.6 4.3 6 83.6 1.3 93.1 90.7 0.0 0.8 4.7 885.5 2.1 95.6 93.3 0.0 0.4 1.9 9 86.9 2.1 95.9 95.5 0.0 0.2 1.7 11 830.5 81.6 95.6 0.6 2.8 14.5 12 85.9 3.9 93.7 90.2 0.1 0.3 1.9 13 85.3 0.987.2 93.1 1.6 3.0 7.3 14 83.1 3.0 94.5 95.4 0.4 0.7 1.4 15 80 1.3 95.487.5 0.9 1.0 1.5 16 81.7 3.1 95.8 77.8 0.3 0.2 0.6 17 81.3 1.5 96.3 79.50.4 0.4 1.3 18 84.1 11.1 87.0 83.9 0.1 0.1 1.6 19 85 2.3 96.9 87.7 0.10.2 0.4 20 85.2 9.9 87.7 88.5 0.3 0.1 2.0 23 86.4 2.0 96.8 90.6 0.2 0.40.6 25 83.2 1.1 97.7 89.8 0.4 0.4 0.3 26 85.5 4.4 94.5 90.5 0.0 0.3 0.827 85.7 1.9 97.3 89.4 0.2 0.3 0.3 28 83.5 2.6 96.8 82.8 0.1 0.2 0.3 3080.7 2.0 97.0 80.5 0.0 0.3 0.7 32 84.3 0.5 97.8 85.6 0.2 0.6 1.0 33 81.93.4 95.8 85.1 0.1 0.1 0.5 34 84.1 1.8 96.5 77.8 0.5 0.6 0.6 35 85.6 1.497.2 75.0 0.4 0.4 0.6 36 85.2 1.0 97.9 76.6 0.6 0.2 0.3 37 84.9 0.7 96.376.1 0.9 0.3 1.8 38 84.0 1.5 96.3 79.5 0.4 0.4 1.3

Example 9

This example illustrates the continuous vapor phase dehydrochlorinationreaction of 2-chloro-1,1,1,2-tetrafluoropropane(HCFC-244bb)→2,3,3,3-tetrafluoropropene (HFO-1234yf)+HCl. Thedehydrochlorination catalyst was 10 wt % CsCl/90 wt % MgF₂.

Conversion of HCFC-244bb into HFO-1234yf was performed using Monelreactor (ID 2 inch, length 32 inch) equipped with a Monel preheater (ID1 inch, length 32 inch) which was filled with Nickel mesh to enhanceheat transfer. The reactor was filled with 2.0 L of pelletized 10 wt %CsCl/90 wt % MgF₂ dehyrochlorination catalyst. Nickel mesh was placed atthe top and at the bottom of reactor to support the catalyst.Multi-point thermocouple was inserted at the center of the reactor. Thecatalyst was pretreated in dry N2 flow for 6 hours at the temperature of480° C. Then the feed with the composition 95GC % 244bb/3.1GC %1233xf/0.35GC % 245cb was introduced into the reactor at the rate of 1.0lb/hr. The feed was vaporized prior entering the reactor preheater. Thebottoms of the distillation column were discharged and recycled into thereactor. The feed rate was maintained constant at 1.0 lbs/hr and bothtemperature and pressure were varied. Temperature gradient throughoutthe reactor was within about 3-5° C. The productivity of the catalystwas estimated at 3-6 lbs/hr/ft³. The highest productivity was observedat 470° C. and 45 psig, and the lowest productivity was observed at 480°C. and 3 psig pressure. The reaction products were fed into the causticscrubber to remove HCl by-product. Then the product stream was passedthrough a column filled with desiccant to remove residual moisture.Oil-less compressor was used to feed crude product into the distillationcolumn that was maintained at 30-45 psig pressure. Distillation wasperformed in a continuous mode and the take-off rate was equal to therate of production of HFO-1234yf in the reactor. The purity of distilled1234yf was 99.9GC %+GC analysis of the distillate showed presence oflight impurities with a ppm level of heavy impurities. The followingconversions and selectivities were achieved:

480° C. at 3 psig—HCFC-244bb conversion˜30%, Selectivity toHFO-1234yf˜97%

480° C. at 20 psig—HCFC-244bb conversion˜47%, Selectivity toHFO-1234yf˜96%

470° C. at 20 psig—HCFC-244bb conversion˜36%, Selectivity toHFO-1234yf˜97%

470° C. at 45 psig—HCFC-244bb conversion˜53%, Selectivity toHFO-1234yf˜96%

460° C. at 45 psig—HCFC-244bb conversion˜38%, Selectivity toHFO-1234yf˜98%

Reaction data. Conditions: Feed 95GC % HCFC-244bb/3.1GC % HCFO-1233xf/0.35GC % HFC-245cb; 2.0 L of 10 wt % CsCl/90 wt % MgF₂ catalyst;1.0 lb/hr feed rate. Time Conversion Selectivity on-stream of HCFC- toHFO- Temperature Pressure (hrs.) 244bb (%) 1234yf (%) (° C.) (psig) 0.2593.30 82.42 484.30 3.00 0.80 67.61 90.38 489.00 3.90 1.43 47.78 94.14479.80 3.50 2.27 31.98 97.34 479.80 3.40 3.32 29.36 97.70 478.80 3.804.32 26.24 97.56 478.70 2.80 5.23 28.45 97.88 480.30 2.90 6.20 30.5398.01 480.30 3.20 6.80 30.91 98.13 478.40 3.30 7.37 28.36 97.88 478.802.90 7.93 29.01 97.84 479.30 3.10 8.48 29.95 97.91 478.30 3.30 9.0526.61 96.76 479.60 2.70 9.62 27.98 96.12 476.80 2.90 10.20 28.84 96.66480.20 3.00 10.70 29.70 97.16 480.50 3.10 11.22 29.30 97.62 480.30 3.3011.72 30.47 97.65 480.70 3.30 12.25 29.57 97.59 480.30 3.30 12.75 29.8397.92 480.00 3.50 13.27 30.10 98.23 479.60 2.80 13.78 28.73 97.02 480.102.80 14.28 29.54 97.31 480.80 2.90 14.80 29.95 98.05 479.80 2.90 15.3029.71 97.98 480.60 3.00 15.80 30.50 98.14 480.80 2.90 16.32 30.68 97.96481.50 3.10 16.83 32.21 97.79 482.50 3.10 17.35 30.37 97.68 478.00 3.2017.85 27.67 97.18 479.20 3.30 18.40 28.06 96.50 477.50 3.20 18.95 27.8496.58 478.20 3.40 19.50 28.85 96.66 482.30 3.40 20.18 32.52 97.55 480.003.40 20.87 29.15 97.47 480.10 3.20 22.90 64.16 97.20 478.90 17.40 23.6547.32 96.23 477.80 17.50 24.32 47.80 96.81 478.60 17.00 25.00 47.4596.83 479.40 16.90 26.02 47.10 96.84 479.50 18.50 26.78 46.99 97.34478.60 20.00 27.38 48.61 97.45 478.80 20.00 28.22 47.00 97.41 477.8020.00 28.93 48.53 96.40 480.00 20.00 29.63 46.61 96.10 477.70 20.0030.23 49.28 96.14 480.80 20.00 30.83 44.30 96.11 477.70 20.00 31.4548.53 96.18 479.50 20.00 32.05 45.03 97.45 477.70 20.00 32.72 48.9497.09 480.10 20.00 33.30 45.10 96.24 478.00 20.00 33.83 46.72 96.25479.70 20.00 34.37 49.04 96.21 479.30 20.00 34.90 46.86 96.34 477.8020.00 35.42 41.57 97.52 474.60 20.00 35.95 38.83 97.44 469.40 20.0036.48 31.20 97.45 468.40 20.00 37.02 34.86 96.45 470.10 20.00 37.5535.41 96.44 470.20 20.00 38.07 37.17 97.71 469.90 20.00 38.63 36.7297.31 471.10 20.00 39.15 36.66 97.68 470.00 20.00 39.67 37.41 97.85470.80 20.00 40.20 36.43 97.86 469.40 20.00 40.73 36.10 97.98 469.2020.00 41.27 35.34 97.97 470.50 20.00 42.05 37.63 96.08 472.00 20.0042.57 38.60 97.20 470.30 20.00 43.12 57.72 96.75 469.60 45.00 43.6553.72 95.42 467.10 45.00 44.17 51.28 94.83 468.70 45.00 44.68 51.6096.39 467.50 45.00 45.20 52.52 96.36 469.80 45.00 45.72 53.43 96.65468.90 45.00 46.77 51.14 95.44 468.50 45.00 48.15 53.38 97.23 470.7045.00 49.32 54.53 97.21 470.90 45.00 50.88 51.94 97.21 469.40 45.0052.35 39.24 97.70 459.60 45.00 53.75 39.15 97.19 459.30 45.00 55.0338.45 97.63 458.30 45.00 56.57 37.19 97.61 457.50 45.00 57.85 37.4497.88 458.90 45.00 58.93 38.18 97.91 458.80 45.00 59.98 37.98 98.04460.10 45.00 61.05 39.77 97.43 463.00 45.00 62.10 42.11 97.92 462.2045.00 63.20 41.11 97.74 459.10 45.00 64.27 39.64 98.05 460.60 45.0065.32 40.98 97.70 461.40 45.00

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove, and all equivalents thereto.

1. A method for isolating a first halocarbon from a compositioncomprising a first halocarbon and at least one second halocarbon whichis different from the first halocarbon, the method comprising: cooling acomposition comprising a first halocarbon and at least one secondhalocarbon at or below the freezing point of the first halocarbon butabove the freezing point of the at least one second halocarbon andrecovering the first halocarbon from the at least one second halocarbon,wherein the first halocarbon is a compound of the Formula (I) or Formula(II), and the at least one second halocarbon is a different compound ofthe Formula (I) or Formula (II) wherein: Formula (I) is a haloalkanehaving the formula C_(y)H_(z)X, wherein X═F_(a)Cl_(b)Br_(c)I_(d) havingone or more halogen atoms, or a combination of different halogen atomsindependently selected from F, Cl, Br, I with the total number ofhalogen atoms equals to 2y+2−z; y is an integer of from 1 to 4; and z isan integer of from 0 to 9 such that z=2y+1; a, b, c, d are each aninteger of from 1 to 10 and wherein a+b+c+d=2y+2−z; and Formula (II) isa haloalkene having the formula C_(y)H_(z)X, whereX═F_(a)Cl_(b)Br_(c)I_(d) one or more halogen atoms, or a combination ofdifferent halogen atoms independently selected from F, Cl, Br, I withthe total number of halogen atoms equals to 2y−z; y is an integer offrom 1 to 4; and z is an integer of from 0 to 7 such that z ranges from0 to 2y−1; a, b, c, d are each an integer of from 1 to 8 and whereina+b+c+d=2y−z.
 2. The method of claim 1 wherein the first halocarbon andthe different second halocarbon are each selected from2-chloro-1,1,1,2-tetrafluoropropane; 2-chloro-3,3,3-trifluoropropene,trans 1,2-dichloroethylene, pentafluorobutane; pentafluoropropane;hexafluoropropane; heptafluoropropane;1-chloro-1,2,2,2-tetrafluoroethane; and pentafluoroethane;1,1-dichloro-1-fluoroethane (HCFC-141b) 1,1,2,2-tetrafluoroethane;1,1,1,2-tetrafluoroethane; 1-chloro 1,1-difluoroethane;1,1,1-trifluoroethane; 1,1-dichloro-2,2,2-trifluoroethane;1,2-dichloro-1,2,2-trifluoroethane; 1,1,1,3,3-pentafluorobutane;1,1,1,2,3,3,3-heptafluoropropane; trichlorofluoromethane,dichlorodifluoromethane; 1,1,1,3,3,3-hexafluoropropane;1,1,1,2,3,3-hexafluoropropane; difluoromethane; chlorofluoromethane;difluoroethane; 1,1,1,3,3-pentafluoropropane (HFC-245fa);1,1,1,2,3-pentafluoropropane; 1,1,1,2,2-pentafluoropropane,trifluoropropenes, pentafluoropropenes, chlorotrifluoropropenes,hydrofluoroethers, and tetrafluoropropenes including1,3,3,3-tetrafluoropropene, 2,3,3,3-tetrafluoropropene,1,2,3,3,3-pentafluoropropene, and 1-chloro-3,3,3-trifluoropropene. 3.The method of claim 1 wherein the first halocarbon and the at least onesecond halocarbon form an azeotrope or azeotrope-like composition. 4.The method of claim 1 wherein the first halocarbon and the at least onesecond halocarbon do not form an azeotrope or azeotrope-likecomposition.
 5. The method of claim 1 wherein a temperature differencebetween the freezing point of the first halocarbon and the freezingpoint of the at least one second halocarbon is about 3° C. or more. 6.The method of claim 1 wherein the result of the cooling is the firsthalocarbon in solid form and the at least one second halocarbon inliquid or gaseous form.
 7. The method of claim 6 further comprising thesubsequent step of separating the liquid or gaseous second halocarbonfrom the solid first halocarbon.
 8. The method of claim 7 wherein theseparating is conducted by decantation, filtration, centrifuging, oroutgassing under vacuum.
 9. The method of claim 1 wherein the separatingis conducted by decantation, filtration, centrifuging, or outgassingunder vacuum.
 10. The method of claim 1 wherein the cooling is conductedat a temperature of from about −150° C. to about 75° C.
 11. The methodof claim 1 wherein the cooling is conducted at a temperature of fromabout −130° C. to about 50° C.
 12. The method of claim 1 wherein thecooling is conducted at a temperature of from about −120° C. to about25° C.
 13. The method of claim 1 wherein the first halocarbon is2-chloro-1,1,1,2-tetrafluoropropane and the second halocarbon is2-chloro-3,3,3-trifluoropropene.
 14. The method of claim 1 wherein the2-chloro-1,1,1,2-tetrafluoropropane and the2-chloro-3,3,3-trifluoropropene form an azeotrope or azeotrope-likecomposition.
 15. The method of claim 14 wherein the result of thecooling is solid 2-chloro-1,1,1,2-tetrafluoropropane and liquid orgaseous 2-chloro-3,3,3-trifluoropropene.
 16. The method of claim 14further comprising the subsequent step of separating2-chloro-3,3,3-trifluoropropene from2-chloro-1,1,1,2-tetrafluoropropane.
 17. The method of claim 14 furthercomprising the subsequent step of separating liquid or gaseous2-chloro-3,3,3-trifluoropropene from solid2-chloro-1,1,1,2-tetrafluoropropane.
 18. The method of claim 17 whereinthe separating is conducted by decantation, filtration, centrifugation,degassation under vacuum.
 19. The method of claim 14 wherein the coolingis conducted at a temperature of from about −85° C. to about −75° C. 20.The method of claim 14 wherein the cooling is conducted at a temperatureof from about −81° C. to about −78° C.